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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e6cabb771sm6339035a91.9.2026.09.19.15.34.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 15:34:31 -0700 (PDT) From: Hui Peng To: 3chas3@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org Cc: linux-atm-general@lists.sourceforge.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] atm: br2684, pppoatm: add missing pskb_may_pull() and headroom checks Date: Sat, 19 Sep 2026 22:34:31 +0000 Message-ID: <20260919223431.3882212-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In net/atm/br2684.c and net/atm/pppoatm.c, verify packet header lengths with pskb_may_pull() on receive and ensure sufficient skb headroom via skb_cow_head() before skb_push() on transmit. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/net/atm/br2684.c b/net/atm/br2684.c index 05712c28386a..4e397b1a3a27 100644 --- a/net/atm/br2684.c +++ b/net/atm/br2684.c @@ -369,8 +369,11 @@ static int br2684_setfilt(struct atm_vcc *atmvcc, void __user * arg) * by device. */ struct br2684_dev *brdev; + struct net_device *net_dev; + read_lock(&devs_lock); - brdev = BRPRIV(br2684_find_dev(&fs.ifspec)); + net_dev = br2684_find_dev(&fs.ifspec); + brdev = net_dev ? BRPRIV(net_dev) : NULL; if (brdev == NULL || list_empty(&brdev->brvccs) || brdev->brvccs.next != brdev->brvccs.prev) /* >1 VCC */ brvcc = NULL; @@ -392,6 +395,7 @@ packet_fails_filter(__be16 type, struct br2684_vcc *brvcc, struct sk_buff *skb) if (brvcc->filter.netmask == 0) return 0; /* no filter in place */ if (type == htons(ETH_P_IP) && + pskb_may_pull(skb, sizeof(struct iphdr)) && (((struct iphdr *)(skb->data))->daddr & brvcc->filter. netmask) == brvcc->filter.prefix) return 0; @@ -449,7 +453,7 @@ static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb) __skb_trim(skb, skb->len - 4); /* accept packets that have "ipv[46]" in the snap header */ - if ((skb->len >= (sizeof(llc_oui_ipv4))) && + if (pskb_may_pull(skb, sizeof(llc_oui_ipv4)) && (memcmp(skb->data, llc_oui_ipv4, sizeof(llc_oui_ipv4) - BR2684_ETHERTYPE_LEN) == 0)) { if (memcmp(skb->data + 6, ethertype_ipv6, @@ -468,7 +472,7 @@ static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb) * Note, that only 7 char is checked so frames with a valid FCS * are also accepted (but FCS is not checked of course). */ - } else if ((skb->len >= sizeof(llc_oui_pid_pad)) && + } else if (pskb_may_pull(skb, sizeof(llc_oui_pid_pad) + ETH_HLEN) && (memcmp(skb->data, llc_oui_pid_pad, 7) == 0)) { skb_pull(skb, sizeof(llc_oui_pid_pad)); skb->protocol = eth_type_trans(skb, net_dev); @@ -479,6 +483,8 @@ static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb) if (brdev->payload == p_routed) { struct iphdr *iph; + if (!pskb_may_pull(skb, sizeof(struct iphdr))) + goto dropped; skb_reset_network_header(skb); iph = ip_hdr(skb); if (iph->version == 4) @@ -489,6 +495,8 @@ static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb) goto error; skb->pkt_type = PACKET_HOST; } else { /* p_bridged */ + if (!pskb_may_pull(skb, BR2684_PAD_LEN + ETH_HLEN)) + goto dropped; /* first 2 chars should be 0 */ if (memcmp(skb->data, pad, BR2684_PAD_LEN) != 0) goto error; @@ -535,6 +543,8 @@ static int br2684_regvcc(struct atm_vcc *atmvcc, void __user * arg) struct atm_backend_br2684 be; int err; + if (atmvcc->user_back) + return -EINVAL; if (copy_from_user(&be, arg, sizeof be)) return -EFAULT; brvcc = kzalloc_obj(struct br2684_vcc); diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c index 5214786e61d1..c3a693e20aba 100644 --- a/net/atm/pppoatm.c +++ b/net/atm/pppoatm.c @@ -397,6 +397,8 @@ static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg) atomic_set(&pvcc->inflight, NONE_INFLIGHT); pvcc->old_push = atmvcc->push; pvcc->old_pop = atmvcc->pop; + if (atmvcc->user_back) + return -EINVAL; pvcc->old_owner = atmvcc->owner; pvcc->old_release_cb = atmvcc->release_cb; pvcc->encaps = (enum pppoatm_encaps) be.encaps;